Recent scientific advances have led to the identification of two hereditary non-polyposis colon cancer genes. The imminent availability of genetic testing for colon cancer risk raises important questions about the knowledge, beliefs, and intentions of individuals at increased risk, the general public, and health care providers, with respect to such genetic testing. This study aims to: (1) identify ethnocultural and psychosocial factors related to intentions to obtain genetic testing for heritable forms of colon cancer in increased-risk and control adults of Caucasian, Japanese, and Hawaiian ethnicity who are living in Hawaii; and (2) identify and describe ethical and social issues and attitudes that may affect intentions to offer genetic testing for colon cancer among health professionals in Hawaii. The first part of the study uses case-control methodology. We will use a mail questionnaire to survey first-degree relatives (FDRs) of patients diagnosed with colon cancer (n=750) and FDRs of age, sex, and ethnicity-matched population-based controls living in Hawaii (n=750). The primary outcome variable will be intentions to undergo genetic testing for colon cancer risk. We will examine the associations of predisposing, enabling, and reinforcing factors with intentions in both cases and controls. Assessment will include sociodemographic variables, as well as knowledge and attitudes about colon cancer and genetic testing, psychological and emotional factors, social support, ethical and social-legal concerns, and risk reduction and early detection practices. The second part of the study will survey physicians (n=875) and nurses (n=875) in Hawaii through mailed questionnaires. The survey will examine factors influencing intentions to offer genetic testing for cancer, including personal and practice characteristics, views about ethical and social-legal issues, and attitudes toward genetic testing. This study is unique and timely because of its multiethnic population, the use of case control methodology, and the potential to establish a foundation for planning culturally appropriate and effective counseling programs related to genetic testing for cancer.